When and why should I choose one over the other? I just want to connect to my wifi from my room which is too far away from my living room access point. I am trying to understand what's more efficient-effective.

Also, this sentence confuses me: The Omega is primarily designed as a development board to prototype WiFi-enabled devices; so i shouldn't be using my omegas to build actual projects but it's meant just to help with first prototyping?

The Omega is primarily designed as a development board to prototype WiFi-enabled devices

I interpreted this to mean that you use the Omega for your development so you can plug in the various modules and once your happy with your final design you can build you own boards complete with the required components. For myself I built my IoT using Omega and will soon ship them with OOTB Pro. I don't love the positioning of some of the components but if it ain't broken....

My own use case is indeed very long term. I use the Omega2 modules in products that run 24/7 and are expected to do that for years (and have successfully proven that in the past two years already).

I find the combination of a well known router SoC (MT7688) running OpenWrt Linux, which is very carefully optimized for exactly such 24/7 networking devices, a very solid foundation to build on.

OnionOS adds a lot on top of OpenWrt to make it attractive also for the "OOTB" experiment type of projects. Still, it's OpenWrt, so most of the networking howtos of the OpenWrt community can be applied.

Plus, if needed, the Omega2 hardware can also run plain OpenWrt, which might be the way to go for pure networking projects.

You can even build your own customized OpenWrt based firmware (that's what I do for my devices).

Thank you so much, your reply is very informative and uplifting! Any suggestion on learning OpenWrt for the first time? OnionOS is my first time using an OpenWrt-based OS! I plan on working on heavily networking-focused projects, mostly IoT!

With OnionOS, everything related to the OpenWrt Web UI (LuCI) does not apply, but on the command line most things should work the same or at least in a similar way.

The set of packages installed by default is different from stock OpenWrt, so getting familiar with opkg and how to add package feeds might be helpful.

The standard network configuration is also different, but the powerful uci configuration management is available and worth learning (IMHO a very clever and efficient solution for cleaning up the mess of many different config files and formats). Also note that OnionOS uses a proprietary wifi driver not known in standard OpenWrt, so for details about wifi you need to check the onion docs.